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Effects of some preservative solutions on vase life in Gerbera jamesonii : a research report presented in partial fulfilment of the requirements for the degree of Master of AgriScience at Massey University, Turitea Campus, Palmerston North, New Zealand

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Abstract

Gerbera (Gerbera jamesonii H. Bolus ex. Hooker) is an important
ornamental flower in global flower market. Consumers are attracted by its bright
colour and beautiful shape; but as with other cut flowers, quality loss after
harvest is a major concern. Moreover, in certain cultivars, its vase life is
dramatically shortened by a stem bending problem. ‘Navy’, an attractive new
variety, caused customer complaints resulting from its short vase life, as a result
of a high incidence of stem bending.
In this thesis, 2 – 6% sucrose was shown to be an effective preservative for
preventing ‘Navy’ from stem bending. Furthermore, deeper research showed
sucrose improved stem rigidity and did so by improving lignification of
sclerenchyma fibres in the phloem caps and interfascicular region.
Once stem bending has been prevented by sucrose, it is also possible to
delay underlying flower senescence. Certain antibacterial materials were tested
and a preservative solution containing 4% sucrose and colloidal silver (3 or 5
ppm) was shown to be the best. This may be mainly due to effective control of
bacteria and resulting reduction in water stress; but also it may delay flower
senescence by inhibiting ethylene action (although most gerbera varieties that
have been tested are ethylene insensitive). Just sucrose and colloidal silver is
sufficient to keep ‘Navy’ flowers alive for three or four weeks; which should be
enough for consumer demand.
There is quite limited knowledge on the mechanism of gerbera flower
senescence. The sequence of ‘Navy’ senescence was shown to involve first a
change in head angle which always occurred on day 11 after harvest. Water
uptake mostly started to be affected from day 13 to 15. Most of the senescenceassociated
colour changes, including the values of ‘L’, ‘a’, ‘b’, began to change
during day 15 to 20. Flower weight generally did not change too much, and
accompanying with water uptake reduced (apart from the first experiment).
Therefore, the results suggest visible initiation of ‘Navy’ senescence might start
at around 11 - 13 days after harvest, so investigations into underlying genetic
regulation would need to start before this time.